78 Merc 850 Cold Start Problem

[bgreg]

Hello, just purchased a 15 foot bass boat with a 85hp Merc. Have to use a shot of Carb. Cleaner to get it started, once running for a while it will restart with no problem. If the motor is off for a half hour or hour you must give it another shot of carb cleaner. The old primer ball felt week so I replace it and picked up a tip about point the arrow toward the sky from another thread but we still have the same issue as before. Do the carbs on this engine have accelerator pumps like a automotive carb would??? Any tips on solving this problem would be appreciated.

Thanks, B Greg

 

[hankll]

Re: 78 Merc 850 Cold Start Problem

I'm not a mechanic, but had some problems with my 76 merc 650. Mine would start, but become flooded. Turned out to be a stator failing. But an experienced mechanic friend of mine, told me to richen up the idle mix 1/8 turn if it seemed to be acting starved, after initial stator replacement, and link and sync that he did on mine. Could be that would help yours. Mine runs like a scalded dog now.

 

[coolguy147]

Re: 78 Merc 850 Cold Start Problem

check spark i believe its flooding.

 

[Chris1956]

Re: 78 Merc 850 Cold Start Problem

Those motors are real cold blooded, however, once they are warm, they should start well. Make sure the primer bulb is pumped up, and when cold starting, put the cold start lever all the way up, and hold the choke button when cranking. lay off the carb cleaner.

Your carbs may be dirty or misadjusted. You should be able to use the choke to gte her starter. If not, you might see if the choke is really working.

 

[bgreg]

Re: 78 Merc 850 Cold Start Problem

Thanks for the responses, forgot to mention, when I first got the boat it had a broken choke linkage. I replaced the linkage and the choke system works fine. I originally thought it was the primer ball, would not get hard like it should, new primer ball and point it upwards till it get hard. Thought we would be all set. Still no cold start. There is no cold start lever on my controls. You push the key in while cranking and the choke solenoid engages closing the choke flaps. Do not like have to use the carb cleaner to get it started but you can crank it for 30 to 45 seconds, even do it a couple of times, still will not start on its own.

Thanks, B Greg

 

[Chris1956]

Re: 78 Merc 850 Cold Start Problem

If you do not have a cold start lever, perhaps you have a throttle only button on the control. If so, for cold start, push the button and advance the throttle an inch or so. It should help with the issue.

 

[bgreg]

Re: 78 Merc 850 Cold Start Problem

Thanks, I have been pushing throtle lever forward almost all the way forward. I will give the inch or two method a try tomorrow.

Thanks for the reply,

Brian G

 

[bgreg]

Re: 78 Merc 850 Cold Start Problem

OK, tried the 1 to 2 inch method same thing. Had my fishing partner try to start the engine so I could watch the choke set up while cranking. Thought maybe it was dropping out when cranked, but it was staying engaged. Would hate to rebuild carbs just to elimate them. Scratching my head about this one. If it was a car I would rebuild the carb and replace the accelerator pump. But from what I understand these carbs do not have an accelerator pump. Starts right up with a little shot of carb cleaner. Hit the throttle and the boat jumps out of the water.

I think my next step is to do the link and sync as hankll suggested, I will have to look that up.

Any other suggestions I could try.

Thanks,

Brian G

 

[bgreg]

Re: 78 Merc 850 Cold Start Problem

OK, tried the 1 to 2 inch method same thing. Had my fishing partner try to start the engine so I could watch the choke set up while cranking. Thought maybe it was dropping out when cranked, but it was staying engaged. Would hate to rebuild carbs just to elimate them. Scratching my head about this one. If it was a car I would rebuild the carb and replace the accelerator pump. But from what I understand these carbs do not have an accelerator pump. Starts right up with a little shot of carb cleaner. Hit the throttle and the boat jumps out of the water.

I think my next step is to do the link and sync as hankll suggested, I will have to look that up.

Any other suggestions I could try.

Thanks,

Brian G

 

[Chris1956]

Re: 78 Merc 850 Cold Start Problem

Brian, You might taks a compression test and make sure you have good readings. Sometimes hard to start is caused by low compression. You also might try a spark quality test. Put a spark plug into a plug wire and boot and hold the ground of the plug to the block. You should hear and see a nice fat blue spark.

 

[Mdub]

Re: 78 Merc 850 Cold Start Problem

You need special carb cleaner for 2 stroke engines. Since the oil in the fuel lubes the internals carb cleaner will strip off the oil leaving the cylinders to years worth of damage in a matter of seconds. Always use carb cleaner for 2 stroke engines.

 

[bgreg]

Re: 78 Merc 850 Cold Start Problem

Brian, You might taks a compression test and make sure you have good readings. Sometimes hard to start is caused by low compression. You also might try a spark quality test. Put a spark plug into a plug wire and boot and hold the ground of the plug to the block. You should hear and see a nice fat blue spark.

Thanks Chris,

Have gauges, bottom plug should be fun to try and get to, spark plug test is easy enough. Can do that while taking readings. Just bought a new set of plugs to have on hand. Figure couldn't hurt to have a set onboard.

Brian G

 

[bgreg]

Re: 78 Merc 850 Cold Start Problem

You need special carb cleaner for 2 stroke engines. Since the oil in the fuel lubes the internals carb cleaner will strip off the oil leaving the cylinders to years worth of damage in a matter of seconds. Always use carb cleaner for 2 stroke engines.

Hmmmmmm, never heard of carb cleaner for two stroke engines. Knew the oil in the fuel lubes the engine, did not think a quick squirt could hurt the engine. Do not want to rely on carb cleaner anyway. Working on getting to start on its own.

Brian G

 

[corm]

Re: 78 Merc 850 Cold Start Problem

Hi,
I would check your oil recycling tubes for cracks.
Your intake port cover bolts.
The welch plugs in the carburetors.
The o-ring seals at the bottom of the throttle shafts
above the return springs.
Also enrichen the idle needles a quarter turn out.
This is a basic list for a hard starting Merc

This year Merc does not have an acc pump.
Also when everything is in good shape
and set right they start great.

 

[Chris1956]

Re: 78 Merc 850 Cold Start Problem

Brian, I installed a brass elbow in my compression gauge. it just allows me to get the bottom cylinder w/o disassembling anything.

 

[bgreg]

Re: 78 Merc 850 Cold Start Problem

Hi,
I would check your oil recycling tubes for cracks.
Your intake port cover bolts.
The welch plugs in the carburetors.
The o-ring seals at the bottom of the throttle shafts
above the return springs.
Also enrichen the idle needles a quarter turn out.
This is a basic list for a hard starting Merc

This year Merc does not have an acc pump.
Also when everything is in good shape
and set right they start great.

Oil recycling tubes?? Are they attached to the carbs??

I will check all nuts and bolts tonight, and all hoses.
Balanced the carbs last week, when I got it it was running rough at low and middle speeds, like a bear at wide open. Also the idle was high, set the linkages for idle speed, still have to back them down a little but is much better than it was. Even set the choke plates, they were a little on the loose side, tightened the nut until I felt resistance and back off just a bit.

Thank you for the advice, will do a bunch of checking tonight.

Brian G

 

[bgreg]

Re: 78 Merc 850 Cold Start Problem

Brian, I installed a brass elbow in my compression gauge. it just allows me to get the bottom cylinder w/o disassembling anything.

Thanks Chris,

I have several gauges, one with a 90 gegree bend in the steel tube. Would prefer to use a gauge that taps into the hole but the push and hold in the hole type work pretty good. Sound like I've got a lot of checking to do.
I will let you know what I find.

I was a auto tech for many years so I am pretty handy, still have big ol' Snap On tool box at home.

Thanks again for the advice,

Brian G

 

[corm]

Re: 78 Merc 850 Cold Start Problem

Oil recycling tubes?? Are they attached to the carbs??
Brian G

No, it goes from the bottom of your crankcase to the top of it on the starboard side of the motor. It is a little thin black hose. It allows unburnt oil that pools in the bottom bearing end cap to be pumped up to you top bearing
for lube and burning. It breaks from age & oil causing a lean condition in the motor.

 

[bgreg]

Re: 78 Merc 850 Cold Start Problem

No, it goes from the bottom of your crankcase to the top of it on the starboard side of the motor. It is a little thin black hose. It allows unburnt oil that pools in the bottom bearing end cap to be pumped up to you top bearing
for lube and burning. It breaks from age & oil causing a lean condition in the motor.

Thanks,

I will check it tonight. Got about 1/8th of a turn when tightening the carbs, check all bolts on the manifold and they where thight. Is there a guide to the link and sync. Saw a discription, need a few pictures to go along with it some of the items list I have never heard of before.

Thanks again,

B Greg

 

[bgreg]

Re: 78 Merc 850 Cold Start Problem

Hi Corm,

Have a question, when moving throttle your distributor retards, the cast plate in front of the carbs the electronics box is mounted to has a boss on it with a hole in it. I was wondering, because the distributor does not return its idle stop, is the suppose to be a return spring attached from the distributor to the hole in the boss. Have a picture I could e-mail that shows the boss.
My e-mail bpg55@integrity.com

Thanks, B Greg